When a fluorescent lamp is operating, a small amount of the electron emissive material held on the cathodes is continually consumed, the rate of consumption increasing with higher lamp current. Additionally, when starting the lamp (or when switching off and on during normal operation), a relatively large amount of emitter material can be dislodged through sputtering. In such cases the start is sufficiently damaging, particularly when using

“cold start” ballasts, to progressively destroy the effectiveness of the emitter and thereby shortening lamp life. A good start will preheat the lamp cathodes so that when the lamp starting voltage is applied, the cathodes are already emitting electrons and the damage through loss of the emissive

material is minimised.

High frequency electronic ballasts of the preheating (warm start) type can give a consistent and highly controlled starting regime so that the effect of switching on lamp life is considerably less marked than that occurring with a glow starter.